The present invention relates to brush seals for use in turbomachinery such as gas and steam turbines to minimize leakage flows and particularly to a flexible heat-resistant magnetic silicone rubber brush seal useful over a wide range of sealing dimensions. The present invention further relates to a flexible brush seal formed of a magnetic material for at least temporarily adhering the brush seal to one of the sealing components to facilitate installation, either as original equipment or as a retrofit.
In turbomachinery such as gas and steam turbines, compressors and turbopumps, a number of seals are used at different locations for minimizing leakage flows. For example, seals may be provided between sealing surfaces which are both movable relative to one another or between components in which one component moves relative to another component, e.g., a stationary housing and a rotating shaft.
Brush seals, particularly in turbomachinery, typically comprise a plurality of elongated wire bristles in contact with a movable, e.g., rotating surface. The bristles provide a tight rub-tolerant seal which experiences only slight degradation over time. The bristles of the seal are compliant in use and this minimizes damage due to transient impact between the sealing components. A typical brush seal is formed by folding bristles over a rod with an outer clamp maintaining the folded bristles, squeezing the bristles between a folded metal plate forming a clamp or sandwiching the bristles between a pair of supporting metal plates and welding the plates and bristles at their proximal ends to one another. The distal ends of the bristles typically project a certain distance from the margins of the backing plates or clamps to engage the opposing sealing component. Common to these types of brush seals is that the bristle holder or carrier is formed of metal which is usually machined with a tight tolerance and thus the brush seal is applicable to only a specific sealing dimension. For other sealing dimensions, e.g., diameters, a separately manufactured and distinct brush seal must be used in order to dimensionally fit the seal with its carrier. Consequently, the brush seals are costly in terms of tooling, manufacturing and installation and long cycle times in brush seal manufacturing and retrofitting are required. Accordingly, there is a need for an improved brush seal where one size fits many different sizes of brush seals. Additionally, there is a need to facilitate installation of a brush seal without use of ancillary jigs or fixtures typically necessary to hold or temporarily secure the brush seal to its carrier.
In accordance with a preferred embodiment of the present invention, there is provided a brush seal having a seal body formed of a flexible magnetic material such as a heat-resistant magnetic silicone rubber material. Preferably, the bristles are embedded, glued or otherwise secured to the brush seal body such that the bristles project from the body, terminating in tips for sealing engagement with the opposing sealing component. It will be appreciated that by bending the magnetic silicone rubber of the brush seal body, the brush seal can fit a wide range of sealing dimensions and complex sealing geometry. For example, where the brush seal is to be applied between a fixed annulus and a shaft rotating within the annulus, the brush seal body may be flexed to conform to the dimensions of the two components. Additionally, by changing the brush bending pattern, the brush body can be used for either outer sealing where the bristles point radially outward, inner sealing where the bristles point radially inward, or axial sealing where the bristles point parallel to the rotor axis. This type of brush seal is particularly suitable for large sealing dimensions, such as forty inches or more. It will also be appreciated that the brush seal body can be flexed or bent into virtually any irregular shape, for example, a non-linear shape other than circular, and thus may be used for sealing between irregularly-shaped components. An example of the latter is a brush seal interposed between a transition piece and a first-stage nozzle in a gas turbine.
Additionally, by forming the brush seal body from a magnetic silicone rubber, the seal may be readily adhered to one of the sealing components. Preferably, the adherence is temporary until the seal body can be finally adjusted and secured in its desired position. Ancillary jigs or fixtures useful to maintain the brush seal body in position while adjustments are being made prior to final securement are entirely eliminated. A magnetic silicone rubber is preferred and comprises a composite material of ferrite magnetic powder and a silicone polymer. With those characteristics, the brush seal body can be bent, twisted or coiled and thus easily configured for installation.
In a preferred embodiment according to the present invention, there is provided a brush seal for sealing between first and second components movable relative to one another and having non-linear opposed sealing surfaces, comprising a brush seal body carried by the first component and having a plurality of bristles secured to the body and projecting therefrom to terminate in bristle tips for engaging the second component, the brush seal body being formed of a flexible material for conformance to the non-linear opposed sealing surfaces.
In a further preferred embodiment according to the present invention, there is provided a brush seal for sealing between first and second components movable relative to one another and having non-linear opposed sealing surfaces, comprising a brush seal body carried by the first component and having a plurality of bristles secured to the body and projecting therefrom to terminate in bristle tips for engaging the second component, the brush seal body being formed of a magnetic material for magnetic attachment to the non-linear opposed sealing surface of one component.
In a still further preferred embodiment according to the present invention, there is provided a method of forming a brush seal between first and second components movable relative to one another, comprising the steps of providing a brush seal body formed of magnetic material and having a plurality of bristles projecting therefrom terminating in tips for engagement with the second component and magnetically adhering the brush seal body to the first component.
In a still further preferred embodiment according to the present invention, there is provided a method of forming a brush seal between first and second components movable relative to one another, comprising the steps of providing a brush seal body formed of a flexible material and having a plurality of bristles projecting therefrom terminating in tips for engagement with the second component and flexing the brush seal body for conformance to the first component.